There is known conventional art for detecting particles in urine samples using a flow cytometer. For example, Japanese Laid Open Patent JPH11-23446 discloses art for classifying several types of particles by detecting forward scattered light and fluorescent light from particles in a sample using a flow cytometer, and plotting the particles contained in the urine sample according to the intensity of the received light on a two-dimensional distribution diagram.
The prior art points out that since many types of particles are contained in urine samples, problems arise due to the mutual overlap of the distribution regions, particularly of erythrocytes and crystals. Considering these problems, the reliability and precision counting of erythrocytes was evaluated by the degree of overlap of the distributions of erythrocytes and crystals.
Since the number of erythrocytes in urine is extremely important information in the diagnosis of renal and urinary tract diseases, techniques are desirable for accurately counting erythrocytes even in urine samples containing a large numbers of crystals. Also, erythrocytes and crystals may be contained in body fluids other than blood or urine, especially in joint fluid. There is also a demand to improve an accuracy of classification of them in body fluids.